visitor prototype extension methods
Visitor pattern
The Visitor pattern defines a new operation to a collection of objects without changing the objects themselves. The new logic resides in a separate object called the Visitor.
Visitors are useful when building extensibility in a library or framework. If the objects in your project provide a ‘visit’ method that accepts a Visitor object which can make changes to the receiving object then you are providing an easy way for clients to implement future extensions.
In most programming languages the Visitor pattern requires that the original developer anticipates functional adjustments in the future. This is done by including methods that accept a Visitor and let it operate on the original collection of objects.
Visitor dofactory – link
Class code: Visitor shapes and tax example
Prototype pattern
The Prototype Pattern creates new objects, but rather than creating non-initialized objects it returns objects that are initialized with values it copied from a prototype – or sample – object. The Prototype pattern is also referred to as the Properties pattern.
An example of where the Prototype pattern is useful is the initialization of business objects with values that match the default values in the database. The prototype object holds the default values that are copied over into a newly created business object.
Shallow copies duplicate as little as possible. A shallow copy of a collection is a copy of the collection structure, not the elements. With a shallow copy, two collections now share the individual elements.
Deep copies duplicate everything. A deep copy of a collection is two collections with all of the elements in the original collection duplicated.
Prototype dofactory – link
Class code: Prototype
see immutable and struct clone here in our blog – blog link
Extension Methods in C#
Extension methods enable you to “add” methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are a special kind of static method, but they are called as if they were instance methods on the extended type. For client code written in C#, there is no apparent difference between calling an extension method and the methods that are actually defined in a type.
Class code: Extension methods example
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